Spinal disorders such as degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumor, and fracture may result from factors including trauma, disease and degenerative conditions caused by injury and aging. Spinal disorders typically result in symptoms including pain, nerve damage, and partial or complete loss of mobility.
Non-surgical treatments, such as medication, rehabilitation and exercise can be effective, however, may fail to relieve the symptoms associated with these disorders. Surgical treatment of these spinal disorders includes fusion, fixation, correction, discectomy, laminectomy and implantable prosthetics. As part of these surgical treatments, spinal constructs, such as, for example, bone fasteners, spinal rods and interbody devices can be used to provide stability to a treated region. For example, during surgical treatment, interbody devices may be introduced to a space between adjacent vertebral bodies (the interbody space) to properly space the vertebral bodies and provide a receptacle for bone growth promoting materials.
More recently, interbody devices have been introduced that provide additional capability beyond static spacing of the vertebral bodies. For example, some devices have expansion capability such that the implant may be introduced to the interbody space in a collapsed state and then expanded to produce additional spacing and, in some cases, introduce or restore curvature to the spine by expanding selectively on only one end or portion of the implant. However, many existing expandable interbody designs utilize internal mechanisms that may inhibit the introduction of bone growth promoting material into the interbody implant by a surgeon after the implant is expanded.
An additional problem exists related to subsidence of spinal surfaces due to existing interbody devices having inadequately-sized load-bearing surfaces. In the case of expandable devices, the loads on the load-bearing surfaces, including loads generated during expansion of the implant, are often significant. An expandable implant with relatively large surface areas is needed to bear the loads, including the loads generated during implant expansion, in an attempt to avoid a need for follow-on surgery due to subsidence of spinal surfaces.
The present invention seeks to address this and other shortcomings in the existing art.